This invention relates to yarns and cords composed of synthetic filaments having a lubricating finish composition on their surfaces. More particularly, it concerns filaments coated with a finish which are particularly useful for industrial yarns and cords used as reinforcement in rubber articles.
Vehicle tires are subjected to stresses and flexes which cause gradual physical breakdown in filaments of reinforcing cords, a phenomenon called "fatigue". Resistance to fatigue can be improved by applying a lubricating finish to the filaments, but it is quite difficult to find a satisfactory finish which does not cause a serious lowering of cord-to-elastomer adhesion. Finish compositions containing a wide variety of oils and added materials have been tried in attempts to obtain adequate adhesion with improved resistance to fatigue.
Several processing characteristics are desirable for a satisfactory lubricating finish composition. It should be one which is readily prepared and is stable on standing, without phase-separation in layers. It should be easily applied to form a uniform coating on the filaments, so a reasonably low viscosity without use of volatile components is desirable to avoid having to dry the applied coating. It should not form appreciable deposits on hot rolls used in after-treatments, since a rapid rate of deposit formation would cause unacceptable process interruptions. It should not fume objectionably on hot rolls used in after-treatments. It should not have a deleterious effect on the normal physical properties of cords prepared for use in tires and other reinforced articles.